Evolution of cavity size and energy conversion due to droplet impact on a water surface

The deformation characteristics of the cavity due to droplet impact on a water surface are experimentally investigated. Dimensional analysis shows that the characteristic values of time, depth, and horizontal diameter can be taken as 10−3 times the ratio of surface tension to the product of viscosity coefficient and gravitational acceleration, the maximum depth, and the maximum horizontal diameter, respectively. The evolutions of the dimensionless cavity sizes for different values of Weber number (We) coincide for 220 < We < 686. A partial-sphere model of cavity is established based on experimental observations. Energy models are then derived, and the energy conversions are calculated to identify the relationship between these conversions and cavity deformation. It is found that the kinetic energy model established under the hypothesis proposed by Leng is no longer applicable when the dimensionless time t* < 3.5, owing to deviations from the geometric model.